I use it for various purposes.
One is on my Psion 5mx. There is an little bit upgraded version of 263
for it and it works. I have to use RSA keys, but can also encrypt to
DH public key.
Decryption is possible only to RSA key and DH and RSA keys should not
be mixed in one msg, this makes the 263 confused.
Other versions run on my dos and w3.1 machines, I use there some
extended versions called 2.6.3 multi created by out friend Disastry
who unfortunately is not with us any more.
There are also plenty GUI around for it, so even pure win users can
survive with it. It is some hundred kilobytes (not Mb or what ever it
uses today) and so portable.
Nice for some bat operations too, comand line all.
But due to some sec risks in the original version, some of theose
patched versions of Disastry might be better choice.