The below answer reflects the current licensing restrictions as of 16/9/2016. It is important to remember that Unity Technologies has the right to change this at any time. They also reserve the right to change these conditions under pre-existing licenses. It is therefore important that you cross-check this answer with the official Unity page, and perhaps even a legal representative, when using this answer as the basis to determine the viability of a particular Unity license for commercial release.
If your company currently makes more than $100k in annual gross revenues or has raised funds in excess of $100k, you are not permitted to use Unity Personal as defined in our EULA Agreement. You may use Unity Pro with an unlimited revenue capacity.
-- Unity Personal download screen
There is also a secondary restriction in the EULA that states that all members of your team must be using the same license.
This means that you can use Unity Personal to release a commercial game, providing that
- Your company1 does not make over $100,000 USD2 a year,
- You are not able to raise over $100,000 USD2 to fund your game and
- If you work with other users, they also only use Unity Personal.
As per the Unity EULA agreement, you are restricted by how much your company makes. This is determined by annual gross revenues (how much you earn before deducations) and raised funds. This is great news, if you are an independent developer. Ultimately, you only have to pay for Unity if and when you can afford to.
Note that the direct quote from the Unity Personal download screen reads that "in excess of $100k, you are not permitted to use Unity Personal (...) You may use Unity Pro". This is slightly misleading. While you may directly upgrade to Unity Pro for an unlimited revenue cap, the licensing page clearly supplies a middle option. We can presume that Unity Technologies are simply trying to "up-sell" in the above quote.
Licensed revenue restrictions are as follows:
- Unity Personal: Allows up to $100,000 USD2 a year.
- Unity Plus: Allows up to $200,000 USD2 a year.
- Unity Pro: Allows an unlimited revenue.
There are also restrictions when it comes to a team. It is simple enough, really. If you are making a game as a team, everybody needs to be using the same level of license. This makes fair sense. You can not simply buy one user license, so that one of your members has access to and can implement the advanced features.
It is worth double checking with your team, if working with other independent game developers. There are more than 3 Unity licenses, including an Enterprise license and an Educational license. It is important to know in certain contexts, other licenses may be made available to a particular user for free. For example, your fellow developer may report not having to pay for their Unity license. This does not mean they have the Unity Personal license. They might be using a Unity Educational license, provided through a college or university.
Upgrading and Downgrading Licenses
As mentioned, you are allowed to upgrade licenses at your discretion. This means that you can simply start with the Unity Personal license, and upgrade to the Unity Pro license when your revenue reaches Unity Personal cap. You are also free to upgrade early, if you decide you wish to take advantage of the additional features.
It is important to note that during your subscription period, this move is one-way. During your "commitment period" (likely the subscription period, given that all licenses are now subscription based), you are not permitted to downgrade to a lower license.
Can I downgrade to a different tier?
No, you cannot downgrade to a lower tier during your commitment period. You can upgrade to a higher tier within your commitment period, however, you cannot reduce the number of seats if you upgrade.
--Frequantly Asked Questions posted on the unity store front page
1 There is no mention of how this may be interpreted for an independent developer, who may be considered a sole trader. In these cases, I can only advise you not to make assumptions, and to seek advice from a professional, such as a tax accountant or a lawyer.
2 I make the presumption that figures are in US dollars, but this seems fairly obvious. The figures do not change with other localisation-based changes, and Unity Technologies is based in San Francisco, California.