The latest version of Ada is available for a (large) fee from Adacore and for free under the GPL. There is also a version published as part of gcc, that trails the upstream version a little in terms of features -- but like the rest of gcc, the relevant parts are under LGPL, so not all binaries distributed to third parties need be distributed under the GPL, but can be under any licence one choose[1] -- without the need for a commercial licence from Adacore.
It would appear the lack of an up-to-date, gratis, version of Ada was a real problem for adoption at some point -- and the impression of Ada being difficult to get access to outside of large contractors put a damper on its popularity (justified or not).
[1] The "problem" with a compiler under GPL is that most compilers will have some kind of library code or language runtime that needs to be distributed with resulting binaries, thus forcing all projects to adopt GPL, rather than just the projects that build directly on the compiler.
