Upgrade forum software

I have a site using a very old version of Invision Power Board software (v2.3.3) and I would like to have new forum software installed without losing old posts or significant member information. The choice of new forum software is up to you, but I require the following: - Free software - Easy to update, preferably self-updating - Security plugins or built-in security updates - Easy blocking of bad bots, etc. - As mentioned before, all old posts and user accounts need to be migrated to the new software - Captcha or similar user account creation security. Preferable: - Easy theming and/or template system. The forums are very rarely used these days, but they have sentimental value (some of the members from there are no longer with us) and so I wish to keep them alive but I don't want the security risks of old software on my server. I think some of this work might be a bit fiddly (taking a database from one format to another) but I don't expect this to be an enormous challenge for an experienced developer that is accustomed to a variety of forum packages. Bidding at the top of my budget isn't likely to get you the job, but mid-range bids will be considered carefully. You will: - Communicate what you need from me in excellent English - Work in a background folder on my site until the forum is confirmed to be functioning with all the old data - Switch the old forum to a hidden folder and put the new forum in its place, so the new forum begins running from the same basic URL as the old one (thread URLs can change as long as the threads themselves are intact) - i.e. In essence, work in the background until it's ready, then put the new forum live in place of the old one - Make a back-up of the data and send it to me, then delete the software and database This is definitely not a rush job. Doing this over a couple of weeks is fine, if needed, what is important is preserving the threads and making the software on my server more secure and ready for easy maintenance in the future. If you can help, please bid!