ICOs on the Bitcoin blockchain
Before Ethereum existed, and ERC20 tokens were the buzzword, ICOs were known as crowdsales or fundraising events. Platforms based on the bitcoin blockchain were invented to enable the creation of tokens linked to a bitcoin address, much like how ERC20 tokens are linked to an Ethereum address. Omni (formerly known as MasterCoin) was such a platform. Counterparty was another and so was Factom.
These platforms also included rules or "protocols" on how other tokens could be created and are generally referred to as "protocols" for this reason.
Tip
Protocol: A rule or way of doing something or, informally in the software world, a standard language that lets a bunch of people on the internet work together on a specific problem.
Omni (OMNI) (formerly MasterCoin)
Omni is an open-source, fully-decentralized asset platform on the bitcoin...