Is Oracle's behavior legal? Yes. Are the support companies in the wrong? Yes. Oracle owns Solaris and gets to set the rules. Is this a smart strategy for Solaris or Oracle? I doubt it. My company was a long term Sun/Solaris customer but when Oracle took over they locked down support and pretty much everything in the Solaris community and started attempting to extract as much cash as they could from us. We weren't the biggest customer but we were a pretty good customer and we weren't a tiny little startup either. Oracle did an excellent job of convincing my management to move to Windows and open source solutions. We stay as far away from Oracle as we can these days. Oracle knows the cost of everything but not the value of a community to support them.
I work in what used to be a heavy Sun/Solaris enterprise. We still use a lot of legacy hardware (up through the T2 processors) but pretty much stopped buying when Oracle took Sun over. We also use a lot of Oracle database software. Oracle's has given up on the lower end and are exclusively pitched at the top end of the market. Sun had a lot of problems with their identity over time but they always understood that they needed to create an on-ramp for their brand by supporting the low end. Oracle's systematically destroyed Sun's market ecology, in my opinion, quite deliberately. As usual Sun's hardware stands head and shoulders above anything else in raw performance and elegance. (As do Oracle database products.) But it doesn't matter unless you need the absolutely highest level of performance. And that's a vanishingly small percentage of the market. My management is interested in elasticity and low capital costs now. The cloud and Amazon Web Services seem to be where Sun used to be in mindshare. Oracle might pull it off, but I've seen absolutely no inkling that Larry Ellison cares about anything other than extracting as much margin as he can from the absolute highest paying customers who share his margins. So, probably the T5 and M5 are too late to matter anymore except for a tiny market that needs 8 cores and 32 threads per CPU and has money to burn on very large systems and support contracts. They'd be pretty much the last vendor I'd consider these days for general computing.