As far as I know the only license which is permitted for use by Microsoft in a shared hardware environment is SPLA. So if this is the case and you want to go total legit then that's the only option. If it's the only VM on that server then you can pretty much use any version of the liense. I...
Didn't start the company as an ISP but branched into it, so at the time I formed it didn't think the name would matter much. But stuck with it.
I think this picture sums it up :
The only downside I could think of are clients that only want 1 months worth of service and don't want to pay 1month+1-2weeks worth. I've been tempted to switch to it, but it would just cause mass confusion.
Also here in the UK, no bill that we have (Utility + other) is pro-rated, so I didn't...
A little back on topic. Looks like there will need to be at least another patch.
Here are some more details:
http://www.webhostingtalk.com/showpost.php?p=9247514&postcount=123
http://arstechnica.com/security/2014/09/still-more-vulnerabilities-in-bash-shellshock-becomes-whack-a-mole/