!OBrowse was originally released as a 'freebie/thank-you' to anyone who had put money into RISC OS developments. It has been updated for the London Show and was also available for sale at 40 pounds (providing a simple way for people who wanted to contribute smaller amounts to the project).
!OBrowse is a front-end for the !Otter port for RISC OS. As R-Comp were very keen to stress, !Otter is not their project and is a free release which no-one has to pay for. What they have written is some code which allows you to run the software in a much more RISC OS friendly way. They are offering their front end as a way to finance their plans (which will also be available as free software to anyone). They have already made an impact by funding one of the ROOL bounties to bring RISC OS networking support up to date.
!OBrowse is not tied to any release of !Otter and does not 'add' any additional functionality. What it does do is make !Otter into a much more compliant and better behaved RISC OS application. It has a proper iconbar entry, can be run to open HTML files or a URL. It can take over all the protocols which use a browser, supports global clipboard, drag and drop, etc It does this role very well and you get a polished RISC OS application which works as you would expect and plays nicely with the rest of the system.
If you are an investor or want to support RISCOS Developments, it is a very nice to have application installed and a no brainer. If you just want to experiment with accessing the internet under RISC OS, !Otter will run perfectly well on your machine without it.