Hi Zhang,
For someone like me, a 'non IT professional' who is nonetheless sufficiently technically minded to want to run his own mail server, but is stretching a bit to put it together himself iredmail/iredadmin is perfect.
I registered 'pro' because I felt you deserved recognition beyond 'thank you' for your efforts. This is after all quite a bit of work to set up.
The new licence terms will do several things;
1) It will raise the barrier to entry. Pro is still a good solution, but it is a less obvious win against the opposition now.
2) It will 'encourage' renewals for those registering after 1/2/2011
3) It will reduce goodwill amongst your existing customers, and probably encourage a switch to 'non pro' - for some of us the choice to move to 'pro' was to say thank you rather than a massive need to have fine grained control.
Personally, losing access to aliases would be a nuisance - but I could do that manually if absolutely necessary.
So whilst I sympathise with your problem, I don't think the solution is to change the licence terms. I just spent some time on the website looking for my initial purchase date to see when I was going to have to choose, and in the end had to look in my email inbox to find the receipt - I am sure I am just looking in the wrong place, but it is not trivial for me to find my 'purchase page', and buy additional options, support or upgrade options - I eventually found the 'buy now' button on admin panel, and found the pricing, but that stuff needs to be really easy to find for the non regular visitor. Perhaps buttons within iredadmin (both versions) to purchase support and upgrade to pro/lifetime/next year - make buying easy and people will buy. Make buying hard, and people won't.
Apple may not be the originator of almost any of the 'tech revolutions' they are given credit for, but they have proved that if you make buying something easier than stealing it then people will buy it (music in their case). Your market place is primarily businesses, the cost is an issue, but it is not a show stopper. Make buying the product as easy as possible and more of your customers will renew.
Just changing the 'stick' by making the licence more restrictive will not achieve what you want or expect.
Personally - renewing WAS a no brainer - come May when it's due; with the new licence terms I will either rely on my existing licence to carry on using 1.2.1 (MySQL) indefinitely, go 'non pro' (and maintain source code access through the GPL, and muddle through with aliases and quotas etc - I have managed my own postfix solution, so can just about cope) or go lifetime upgrade and maintain access to source through your concession above within the newer more restrictive licence.
The choice is now non trivial, and will involve me re-surveying the market place.
I want to support your project, it is technically excellent, and architecturally brilliant - but I won't be shoe horned into a situation where I go back to no code visibility - once the code is hidden then the quality degrades. You may be the exception to the rule, but the rule is strong enough that I am slowly migrating our entire business across to open source or similar, so that I don't get lock in.
Anyway, just my input - I want iredmail to continue to grow, as the more successful an eco-system you develop, the better a product I benefit from.
All the best,
John