Re: Licensing Questions

[Niklas Holsti <niklas.holsti@tidorum.invalid>]

On 12-10-20 20:18 , aditya siram wrote:
> Hi all, Having looked at the Alioth benchmarks I'm looking into Ada
> as an alternative to C++ but I'm totally confused by the licensing.

I'll take a shot at answering you. I'm not a lawyer, and my
understanding may be incorrect or incomplete, but here is how I
understand it.

> It seems like there's two entities GNU and ADACore both offering the
> a compiler/runtime but with different restrictions

The GNAT compiler is available with three different licensing schemes:

- GNAT Pro from AdaCore. Expensive, but you can distribute your Ada
programs in binary form (for free or for a price) without distributing
source. And you get support from AdaCore.

- GNAT GPL from AdaCore. Free beer, but with pure GPL, so can be used
only for developing GPL programs.

- GNAT from the Free Software Foundation (FSF; I think this is what you
call "GNU GNAT"). Free beer, and the compiler itself is under GPL, but
the programs that you develop with the compiler are not, because the
libraries use a modified version of GPL that lets you use the libraries
in non-GPL programs.

I use FSF GNAT to compile SW for which I sell binary-only licences in
the traditional fashion.

> so please excuse these simple questions:

> - How are the two products different? Are they just the same codebase
> with different support models?

The codebase is roughly the same; GNAT Pro is most advanced and is
frequently updated. GNAT GPL is a a snapshot of GNAT Pro taken yearly
(more or less). FSF GNAT is maintained by the community but receives
updates from AdaCore (tracking GNAT Pro) now and then.

> - Can I develop commercial closed-source libraries and software using
> the GNU version of GNAT?

With the FSF GNAT, yes. The Debian platform has excellent support for
FSF GNAT, thanks mainly to Ludovic Brenta. For MS Windows, MinGW
provides FSF GNAT (as I understand it). It seems to work, too.

> - Will there be compatibility issues between GNU GNAT and Adacore
> GNAT beyond missing Ada 2012 features?

On the Ada source-code level, for application programs, I don't expect
any compatibility problems.

On the internal level, the ASIS tool-set depends on GNAT internals and
must be closely matched to GNAT, version by version. You cannot use the
GNAT GPL version of ASIS to access compiled code from FSF GNAT. Also, I
would hesitate to mix object code from different GNAT versions in the
same link.

> - Is AdaCore the only company working on GNAT right now?

Yes, for the PC targets, as far as I know. There have been some
companies that have developed off-shoots of GNAT for embedded systems,
for example the XGC company in the UK.

> - Are there performance differences between the two compilers?

Could be, since GNAT Pro is the "wavefront" and so probably has more
evolved optimizations than the other versions.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
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