license isn't same as ruby license

[lksv]

It seems that this gem has the same license as ruby (https://github.com/ruby/rdoc/blob/e2dec097f2086cc7df564dda51f5f95bc431cbfa/rdoc.gemspec#L29) but it is not true:

snippet of rdoc license:

You can redistribute it and/or modify it under either the terms of the GPL version 2 (see the file GPL), or the conditions below:

ruby license:

You can redistribute it and/or modify it under either the terms of the 2-clause BSDL (see the file BSDL), or the conditions below:

I think this is an mistake. Ruby changed the license in time (see https://github.com/ruby/ruby/commit/2cd6800fd8437b1f862f3f5c44db877159271d17#diff-7116ef0705885343c9e1b2171a06be0e)

My intention is not to push to change the license if you do not want.

[zzak]

It's not really my call, but my guess is we just copied over the old Ruby license and when it changed, we never updated RDoc's.

/cc @drbrain

[drbrain]

Ruby license means different things for different versions of ruby.

We'd need to get Dave Thomas and other contributors consent to change the license to the latest version of the Ruby license.