In the above postings mungbeans remark

Are your clients technical enough to get any benefit out of this?

is probably the most important one (at least in my ears). Since you're selling the setup for a website and maybe the major rearrangements and changes your clients are probably people who can't do this for themselves. Thus by opensourcing your code you'll just adress others that won't be your clients anyway. And then I can tell you that providing a tool that maintains a website will results in almost no feedback at all. When I gave my w3make to the world exactly one guy out there sent me an email asking this and that so he obviously used the program (BTW I don't know whether he uses it still).

So I'd say that you won't cut your own flesh by opensourcing your code. Just be careful with the name you choose! ...

Regards...

Stefan