I'm one of the core developers of the GEO Protocol.
There are several differences between GEO and interledger:
1. GEO attempts to provide stronger guaranties about operations atomicity for the whole payment path.
We contacted the interledger team in a past, and as we know right now, interledger delegates disputes between 2 parties (nodes) to their own (for example, via trusted timestamp servers for sync purposes, third-party arbitrator, etc).
This approach potentially leads to loss of money by some middleware node(s) in case if it was too late to process the transaction.
The GEO protocol attempts to process operations without any third-parties involved, and to provide stronger guaranties for all participants, that operation would be committed or rejected on the whole payment path atomically (but delayed in time), and only fallbacks to some kind of arbitration in case of potentially fraud operations.
2. GEO protocol forces nodes to provide their quantum-resistant crypto-signes for each one operation, so in case of any disputes (or malicious data manipulations) - it is slightly simple to achieve consensus on each one particular trust line, and each one operation.
3. GEO-protocol is modular and provides several stacked solutions.
There are protocols for p2p network communication (lightweight, UDP based), near-real time payment flow prediction, nodes discovering, NAT traversing, payment processing, etc.
In comparison to Ripple:
1. GEO doesn't relies on gateways eco-system. As a result - there is no need in high-level gateways moderation.
2. GEO provides common infrastructure for equivalents for whole network. In contrast with Ripple, there are no Gateway-related equivalents in the network, but the globally available equivalents, and each one participant (node / or even gateway) is able to decide to "join" it.
3. GEO provides near real time payment flow prediction for up to 7 nodes in the path.
4. GEO is not block-chain based, and uses local consensus model, so it is pretty light for the modern smartphones.
As a result - GEO is focused on ability to work properly in cell-phones networks, and to empower communication directly between devices.
5. GEO attempts to be quantum resistant, and does not use potentially risky RSA/DSA and descendant/similar algorithms at all.