My work around to this whole problem was to remove php, horde and imp, then reinstall php4. Once that was done, perform the "yum update" and when everything was complete I ran "yum install horde imp" then updated to PHP5 again. Everything is working fine. So why is SME forcing users to use PHP4 -- an version that's no longer support by its developer!?
All this is doing is limiting the SME users to what SME wants to provide, not what SME needs to provide.
The same goes for MySQL. I'm running both MySQL 5 and PHP 5 with SME 7.4 -- all works fine and without any work-arounds.
It has been said many times before... The development time and number of developers is limited as well as the budget. All is done in free time.
The goal of SME Server is to provide a stable, secure small business server. Not to be a otp notch hosting server with all stars and bells. To keep the system as stable and secure as possible with the limited resources the developers stick to the mother distribution as close as possible (which in the case of SME Server 7.4 is CentOS 4.7, SME Server 8 is based on CentOS 5.2).
CentOS in turn is based on RHEL.
About the packages not being supported you are wrong. AFAIK bug fixes and security fixes are still released by RHEL and subsequently passed down the chain to CentOS and from there to SME Server. The PHP and MySQL packages on SME Server are the same as on CentOS.
If you really desire PHP 5 and MySQL 5 you are better of installing a RHEL or CentOS machine yourself or put forward time or money so we can implement it on SME Server in the long term, but you should keep in mind that this means a lot of more work and higher workload for the severly limted deveopment team.
Oh and BTW, try to do some investigation before posting criticism like this as these questions have been answered multiple times in the forums.