Right now the Perl5 codebase has stopped being developed (at version 5.8.0)

Absolutely not true. 5.8.3 came out just a month ago, and work definitely continues on perl5. I don't see this changing any time soon.

The problem is that Perl5 code will not run on Perl6 without translation

Also not true. Thanks to Ponie, perl5 code should run side-by-side with perl6 code on Parrot.

Another downside to Perl is it's [sic] *apparent* lack of market share when compared to PHP.

The only thing that matters is whether there is a large Perl community. Pissing contests about market share are just that -- pissing contests. I don't see the Perl community going away any time soon. Besides, if market share was all that mattered, we'd all be using MS Windows and VB.

That said, I'm not sure it matters. This person apparently doesn't care enough even to do some basic fact checking, so how much logical argument can convince him to change his mind?

Update: after reading the forum hossman linked to at Re: Perl myths ?, I feel even more that we're wasting our time talking about this. There doesn't appear to be much serious research or comparison going on there. Their decision does not appear to be based on technical merits. In light of this, PHP might well be the better language for this project.

Their comments about PHP being "much faster" and putting a lighter "load ... on the server" than Perl strike me as particularly funny. There's lots of anecdotal evidence, and nothing in the way of specifics or technical details. They don't even mention the differences between CGI, mod_perl, and mod_php. Again I repeat: there's not much point here. I'd be happier just to leave these people alone.

Update: I might have spoken too soon. Some of the later posts bring up some of these issues. So my criticisms might not be well-founded, but my main premise stands: let the folks who will have to work with the project decide its fate.