Technically, the restrictions only apply after a capture and only if you choose to move the same piece for the second move. Sort of a checks and balances type of thing.
Knights are kind of special to begin with. They don't really have "lines" or "paths", rather they have landing sites. Without a capture the Knight may go anywhere it can legally reach on it's second move that is not blocked by friendly or unfriendly pieces. So (assuming all potential landing squares are clear) a knight has all 8 squares free to move to after it's first move, and if it captures on it's first move then it has 7 places it can go since it can't return to the square it attacked from.
The restrictions on movement after capturing helps to balance the game and imparts an element of danger when you can't just strike out from a safe position and then simply return to safety every time. The reason for limiting the attack to the first move also helps maintain balance. If you are allowed to capture on the second move a checkmate condition is more likely too early in the game and really doesn't make the game any more fun.
However, if you are simply going to move one piece twice for the sake of positioning, then the board is your playground. If you want to sandbag your two moves by moving and returning to your original place, so be it, you just can't do that after a capture.
The ability to make two captures in one move is still there, so long as you use your two moves with two pieces moving once each.
Keep in mind that you can't really cover another piece very reliably, as you can in standard chess, because someone can swoop in and capture it, then run away.
As for the names, it was originally dubbed RuneChess, but that was simply because I ran a BBS by the name of RuneStone. Hit and Run Chess is the name that best describes the game. Calling it Pirate Chess sort of just happened and is a bit more enigmatic and fun. I run gaming for a local con called ShadowCon and there was a local Cosplay Pirate group, so one year I put it out as Pirate Chess and it sort of stuck.
Technically, the restrictions only apply after a capture and only if you choose to move the same piece for the second move. Sort of a checks and balances type of thing.
Knights are kind of special to begin with. They don't really have "lines" or "paths", rather they have landing sites. Without a capture the Knight may go anywhere it can legally reach on it's second move that is not blocked by friendly or unfriendly pieces. So (assuming all potential landing squares are clear) a knight has all 8 squares free to move to after it's first move, and if it captures on it's first move then it has 7 places it can go since it can't return to the square it attacked from.
The restrictions on movement after capturing helps to balance the game and imparts an element of danger when you can't just strike out from a safe position and then simply return to safety every time. The reason for limiting the attack to the first move also helps maintain balance. If you are allowed to capture on the second move a checkmate condition is more likely too early in the game and really doesn't make the game any more fun.
However, if you are simply going to move one piece twice for the sake of positioning, then the board is your playground. If you want to sandbag your two moves by moving and returning to your original place, so be it, you just can't do that after a capture.
The ability to make two captures in one move is still there, so long as you use your two moves with two pieces moving once each.
Keep in mind that you can't really cover another piece very reliably, as you can in standard chess, because someone can swoop in and capture it, then run away.
As for the names, it was originally dubbed RuneChess, but that was simply because I ran a BBS by the name of RuneStone. Hit and Run Chess is the name that best describes the game. Calling it Pirate Chess sort of just happened and is a bit more enigmatic and fun. I run gaming for a local con called ShadowCon and there was a local Cosplay Pirate group, so one year I put it out as Pirate Chess and it sort of stuck.