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Perhaps Boost shouldn't reinvent the wheel? There's already an open-source arbitrary precision arithmetic library: http://gmplib.org/

Which says: GMP is distributed under the GNU LGPL. This license makes the library free to use, share, and improve, and allows you to pass on the result. The license gives freedoms, but also sets firm restrictions on the use with non-free programs.

There are people using Boost for both free and non-free programs. It's my understanding that we (Boost) want to continue to support all of them.

Personally, I think Boost would be best served providing some sort of expression template wrapper into which different arbitrary-precision numbers could be plugged.

We (Bruno and me) are creating exactly this thing. It will be finished soon. We will use it in our other library, GGL, but we develop it separately.

That would mean far less work to get something usable, as it could use the GMP implementation initially. We do GMP, CLN and IEEE (so float/double/long double). So the code using the library will be independant of which numeric type is used, and can use it also for standard numeric types transparently. Then a BSL version of the implementation could be developed incrementally, while non-floss users could license some implementation to use with the Boost interface.

Regards, Barend p.s. I intentionally send this to the other list because it is a "developers subject" and because my messages don't come through.