I've finished coding (but not yet fully testing) the code to import posts from this site - attachments included of course!
It's in testing at the moment. Due to the need to parse HTML it's a lot slower than the LemmingsWelt and IsaMedia codes were; whereas those generally took about 3 minutes each to run, the first "dry" (ie: not actually uploading, just generating output files) code of this is currently about 10 minutes into running and only up to the Level Designing board's second page. Still, it seems to work now, based on smaller test runs (only importing a small selection of posts instead of the entire forum). If the output from this looks decent, I'll do a small import test run of actually importing a few topics to the new board (which will of course be cleared after being confirmed as working, to avoid duplicating them when the full import is done).
One thing I haven't implemented yet is the timestamp. In order to keep this simple, I'll need to get a new download of the site with a couple of timestamp-related settings changed. So, at some point, the timestamps on this board are going to have to be changed to "YYYY-MM-DD HH:MM:SS" format, without the special display of "Today" and "Yesterday". This will have to be done on two occasions, both of which a full download of the site (which takes a couple of hours) will have to be run:
a) At some point to run a test run *with* timestamps.
b) When we do the actual final import.
My apologies if this is inconvenient to anyone, though it shouldn't be a major issue.
Note that about the timestamp thing; if you have a custom timestamp format enabled in your account settings, you don't have to change this. It's just how *guests* view it that must be changed (which also gets applied as the default for anyone who hasn't set a custom one).
I haven't done anything on the importing PMs yet. If you make backups as ccexplore described, you've at least got them in some form; I can sort out doing something with this later. The way I see it, although it is something I want to deal with eventually, it's a less critical issue than the posts themself and thus I'll deal with that once posts are fully handled.
EDIT: It appears the import posts code is successful on a "dry" test run. I'm going to now do a proper test with just 2 or 3 topics (including some attachments).
EDIT: The results are somewhat successful. A few tweaks and it should work better... Specifically, no problems at all with the post's content - it imported fine - but attachments are somewhat faulty.
EDIT: Complete success has now been acheived.
The only remaining todo is to add code for handling the timestamp.
EDIT: The date format has been changed as mentioned above, in order to do the first test run. I will change it back when finished; but if you want to display dates normally in the meantime, go to Profile > Account Settings > Look and Layout, and enter this in the Time Format input box:
%B %d, %Y, %I:%M:%S %p