Don't be so sensitive. I operate a myriad of not-for-profit websites myself for which I get little to no thanks as well.
It is quite simple - if VirtueMart 1.1.x is listed as supporting PHP4, then there is a basic expectation that it will be tested on PHP4 and that it will be compatible. That is not an unreasonable expectation.
If this is not possible, then the update must clearly notify users that it will break PHP4 compatibility, to allow them to decide their next step - whether to try it anyway, update to PHP5, or move away from VM.
I realise this is free software, but if it wants to be taken seriously then it's a fairly basic requirement that a security release not break compatibility unless absolutely necessary - and if it does, that fact be noted very clearly. Any moderately professional software developer would agree with that, and my posts are merely trying to make you aware of this oversight so that the appropriate changes can be made - either adjust the release to fix the compatibility issue, or advertise the change in supported environment.
At the end of the day, the VM team can either take that on board... or get defensive the moment anyone suggests they may not be perfect, refuse to change anything and just alienate other users who can't get it to work and have no idea why.