Hi
Initially what was happening was that development occurred in the trunk. Then there would be a pause in development, a round of testing and something considered stable would be tagged, zipped up and made available as a download. Usually the trigger for pushing out a release would be the need for some new feature in the warehouse. Usually, to support that new feature, there would be a corresponding upgrade needed in the client software but backwards compatibility with previous client software was always maintained.
Now, needless to say, we might tag a release like 0.6.1 and then discover it still contained bugs. Meanwhile development would have started up in the trunk again. We'd have to fix the bugs and patch our servers and the resultant code would go in to a branch, 0.6.2 in this case. Thus the latest branch would contain the most stable available version of the code.
Now recently I guess development was going on at break-neck speed yet there must have been some need to push out a new feature so what happened was that a branch 0.8.0 was created and tested while development continued in the trunk. However, it was never tagged or bundled for download. When subsequently bugs were found in it they were fixed and branch 0.8.1 came in to being. It is now the most stable available version of the code.
It is a fact that one or two new features have been copied from the trunk in to 0.8.1 so that they could be moved on to our servers. John's pragmatism slightly at odds with my puritanism there.
In summary, tags are releases; branches are bug-fixed releases and trunk is your bleeding edge. This is a slightly abnormal way of doing things because the branches are not frozen so branch 0.8.1 today may be different from what it was yesterday so, when you say you have version 0.8.1 installed that doesn't actually give us unambiguous knowledge of the code you have installed.
Because we strive for backwards compatability using a client (e.g. Instant Indicia 0.7.1) that is an earlier version than the warehouse should be safe.
However, in Fiona's case, using a client that is a more recent version than the warehouse could possibly cause problems as the client may try to use features that do not exist in the older warehouse. You may not encounter a problem but my advice would be to use the 0.8.1 branch of the iForm module.
Regarding an upgrade to Instant Indcia, Charles, such a thing has not been carried out yet. For sure there would be actions involved similar to upgrading Drupal modules but I'm not sure what else. I'm not conversant with how Instant Indicia works. Myself, I just use the iForm module and, recently, the EasyLogin module.
Jim Bacon.