It's not an alternative if it does not meet the necessary conditions for use.

Companies have exclusive control of their own products basically by definition. Claiming that there's some sort of monopolistic behavior inherent in a company deciding where and how you can buy their product is absolute shark-jumping.

That's a poor definition. Many companies are regulated in a manner where their services must be open to competition to access and use.

Almost no companies are regulated in this manner.

Sure they are; look outside the USA and you'll find many the world over. For instance, Canadian telecoms must provide access to their networks at minimal wholesale prices for competitors to enjoy.

The USA simply isn't a leading innovator in this regard.

This is an incredible jump. By this logic, literally any format or given protocol can be called into question if it isn't 100% transferable between all platforms. That basically renders everything newer than line telephones, email and SMS as monopolistic.

Hell, even the different cellular carriers fail this definition because you can't use a Verizon sim card to access AT&T.

Only if the provider has reached a market position where their behaviour can adversely effect captive users.

The Verizon/AT&T comparison is interesting; because it wasn't so long ago that phones were locked to carriers.

Regulation could and should pry open the private networks of large software companies to facilitate healthy competition.