Re: Can I use CRoaring library in Git?

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 17, 2022, 22:00 UTC
Message-ID: <xmqqzgh7v1q3.fsf@gitster.g>
In-Reply-To: <e574ac20-c287-c395-5bc3-b481d81764c7@gmail.com>

Kaartic Sivaraam <kaartic.sivaraam@gmail.com> writes:

Show 8 quoted lines

> The EWAH case is a bit different. The original EWAH implementation
> [ewah-cpp] was in C++. It was then ported to C [ewah-c] by Git
> contributors [ewah-git]. The ported version has been relicensed under
> GPLv2 with Deniel Lemire's permission.
>
> The case with CRoaring is that the implementation already exists in C
> [croaring] and that is the one which is licensed under Apache V2. I'm
> not sure how relicensing works for already existing code.

As long as the author says they are willing to relicense, that would "work". It is entirely up to them.

> I suppose we could enquire Daniel Lemire about using the Apache licensed
> code for Git. Let's hope for the best.

Request to relicense it so that we can use it in our GPLv2 project. Relicensing it under GPLv2, MIT, or BSD, would work for us.

Assuming that we can clear the licensing issues (or we can write our own implementation from spec), how would the transition plan look like? Does our bitmap format carry enough metadata to allow existing clients who never saw anything but ewah bitmaps to say "ah, this bitmap file uses encoding I do not understand" and gracefully fall back to not using the bitmap?

Thanks.