Changing the BitKeeper License and Why it is Needed

Note about BitKeeper

Due to recent (as of 13 April 2005) developments, the information contained in these pages, may no longer be fully relevant. Refer to our summary page about this for more information.


As was seen in the "Suitability of BitKeeper for Free Software Developers", the BitKeeper License and its dynamics prevents it from being employed for free software projects. This is unfortunate since Larry McVoy's original intention was that BitKeeper would eventually be adopted by all free software projects out there.

In this document, I will show that the restrictions on the BitKeeper license have other bad side-effects as far as BitMover is concerned. I believe that in order for BitKeeper to be widely deployed and become a popular replacement for CVS, its license needs to drastically changed. Take notice that I do not suggest making BitKeeper fully open-source (see below), but the majority of developers out there will have no problem using a solution that is only almost open-source.

Life and Death in the Hands of the License

There are several examples that show that the choice of a license is the most important choice a project can take. Linus Torvalds claimed in an interview with him that "making Linux GPL'd was definitely the best thing I ever did". Many people claim its GPL nature gave Linux a very good advantage over the BSD-licensed BSDs.

There is another example: MySQL. MySQL emerged at a time when the two available SQL database systems were Postgres, which was BSD-licensed and quite heavyweight, and mSQL or Mini-SQL, which was lightweight, with a reduced functionality, freely distributable but required a license. MySQL started as an internally used database by T.c.X DataKonsulter, a Swedish consultants company. They decided to release it as shrinkwrap as a not fully free but usable license, that required no payment for deployment on UNIX. As a result, MySQL became very popular and is the most widely used Database server today.

So popular that many web applications (including one of my own) depend on it and would not work with any other application. This is partly due to the fact, that programmers work directly with the MySQL specific API, and partly due to the fact that writing SQL that is portable between various databases is surprisingly hard and many times one have to rely on proprietary extensions. When was formed to maintain the database, its investors requested that MySQL would be made open-source, so they will have a guarantee that it remain accessible for use in case something happens to the company. MySQL AB released it under the GPL.

Now, I believe releasing MySQL under the GPL in the first case would have caused it to flourish, but there would have been little possibility to earn money out of it for T.c.X/MySQL AB. By having conquered the market first and then only GPLing it, MySQL was able to gain a market dominance while still eventually being able to open-source the code.

I think a similar analogy can be made to BitKeeper, which while being a relatively successful commercial product, has yet to be widely deployed among open-source developers.

Note that I'm not one of those people who believe the GPL is ideal for everything. I think every project has an appropriate license depending on the niche it is trying to fill. For example, I believe the Public Domain was a very good choice for Freecell Solver (shameless plug) because it made it an excellent choice for vendors of freeware and shareware Freecell implementations who cannot comply with the restrictions of the GPL. Similarly, I believe the change of Wine's license to LGPL was a mistake and that they should have kept it as X11.

BitMover's Intentions

BitMover wishes to make a land-grab on the market of Software Configuration Managements systems and revision control systems. However, there are in fact two markets here. The first is that of companies who are used to pay a lot of money for such solutions (such as ClearCase or Perforce). The second is that of open-source projects and of companies who will not pay a dime for it.

Getting hold of the former should be quite easy since BitKeeper is much superior to the current competition. However, the free-users will not fall so easily. After all, CVS is fine - it is reliable, and many very large projects were managed with it. It has its limitations, but is still nice to work with. And then there are Open-Source alternatives (Aegis, Subversion, Arch, etc) - which are better than CVS, to choose from should you want something better.

These clients will not use BitKeeper out of technical superiority alone. No sir! They will need it to be accessible and free enough to use so it will replace their convenient CVS deployment. If BitMover wishes to get hold of this market it needs to make sure BitKeeper is not only programmed write, but also licensed right.

A Glimpse into the Future

Let's suppose the development of BitKeeper is present at point x=3.0 and advances in speed 2t. Now let's suppose the development of Subversion is at point x=1.0 and advances at speed 1t. (this is a worst case scenario). However, the license of BitKeeper prevents it from being deployed by free software developers.

Thus, BitKeeper would probably become the next ClearCase. (albeit probably, a better one) Subversion (or something else) would become the next CVS. Fair enough.

Now for two questions:

  1. Do you use ClearCase at home for your pet projects and revision control needs?
  2. Would you recommend ClearCase for your small workplace?

In the history of revision control systems, many of them went into oblivion. SCCS, for instance. The Google Configuration Management Tools directory lists many such implementations most of them are yet to make a difference somewhere. SCCS died because it was made proprietary by AT&T and replaced by RCS and later on CVS. BitKeeper may might as well be a footnote in the history of SCMs, something very good that persisted for a while until superseded by something better or more readily available. Like ClearCase.

Why McVoy's Attitude Towards Free Users is Wrong

The BitKeeper gratis license forces the user to upgrade to the newer version should it come out. Furthermore, the license may be changed between version to version. The new BitKeeper License contains other restrictions such as a non-compete clause or the fact the the source inside the repositories must be made available under a free software license. And naturally, the source code is not available, because someone may patch it to remove the OpenLogging restrictions.

McVoy placed all these restrictions to prevent people from abusing BitKeeper. What he does not realize that they would have abused it with or without these restrictions, and that he is only harming free users who are are doing nothing wrong but somehow are affected by these restrictions. Moreover, it it very improbable that the abusers would become paying customers. Most vendors of commercial, internal, embedded or hardware-accompanied software, would either pay for BitKeeper or use something else free-of-charge like CVS, Subversion or Aegis. Those who don't respect copyright law enough to do so, can hardly be expected to become paying customers.

Requiring the source to be published under a free software license is draconian. Many times, free software developers keep not-so-free content in the repositories, which they did not originate with. Other times, the software is close to being open-source but not quite. OpenLogging and a requirement that the repository be made online is enough. Even if the contents are proprietary (and just sourceware), a person should be able to use it. That's because he would pay should he wish to continue using BitKeeper while keeping the source for himself.

The non-compete clause is especially useless. Even if I'm a developer of a competing solution, using the BitKeeper binary will only help me learn about its features. Even the source would only be enough to learn about how it is implemented as I cannot directly use the source in my project, legally and practically. (the codebases may be completely different)

To sum up, all the restrictions that were added to BitKeeper along the way, would not protect it from being abused, but would harm those users who wish to happily use it, without doing anything wrong.

A Utopian Vision

  1. BitKeeper is distributed as part of major distributions such as Red Hat, Mandrake, S.u.s.e.
  2. BitKeeper is the most commonly used revision control system in the open-source world, replacing CVS.
  3. BitKeeper is deployed in many software houses who pay for licensing for it.
  4. BitMover is flooded with patches contributing functionality to BitKeeper, some of them of very high quality. Thus, development is much more rapid.
  5. BitMover is very successful and the size of Rational.

How is it possible? By changing the license to make sure users can continue using older versions, even modified. Removing the non-compete clause and other irrational restrictions. Revealing the source code is optional, but will do good in the long run.

BitMover is profitable now, which is good. But if Larry McVoy wishes to make a greater difference he has to look beyond the near-term short and false corporate interests, take a chance and make sure BitKeeper is present everywhere. This cannot happen with its current licensing scheme. Without it, BitKeeper would never become the next CVS, which was his intention in the first place.

"Far better it is to dare mighty things, to win glorious triumphs, even though checkered by failure, than to rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory nor defeat." (Theodore Roosevelt)

The choice McVoy and Co. must make is now. Subversion and other open-source alternatives may not be feature by feature compatible with BitKeeper at present, but they may become so in the future. There were times where an open-source project surpassed the functionality of a proprietary alternative, even though seemingly the latter had more resources at its disposal. This may happen to BitKeeper. Or just most open-source developers would settle for something less able.

I am already involved in Subversion, and while it progresses slowly, there are many interested developers there. The limitations of CVS and attempts to resolve them are the talk of the day in several Internet forums I subscribe to, or visit. If enough people want something better than CVS and Open-Source or something similar, you can be sure they get it. The question is whether it would be BitKeeper.


Platforms - an article by Joel Spolsky that explains how a platform vendor should ship his platform.

The Suitability of BitKeeper for Free Software Developers