Merge pull request #6 from uma-universal-money-address/feat/addlnurlc…

…ompat

Add a note about lightning address interop.

umad-01-addresses.md

@@ -1,7 +1,7 @@
 # UMAD-01: UMA Addresses
 
 The UMA address format is based on Lightning Addresses ([LUD-16](https://github.com/lnurl/luds/blob/luds/16.md)), and
-are themselves valid LNURL Lightning Addresses. They are in the format _$\<username>@\<domainname>_
+are themselves valid LNURL Lightning Addresses when the $ is stripped. They are in the format _$\<username>@\<domainname>_
 (eg. _$[email protected]_). Similar to Lightning Addresses ([LUD-16](https://github.com/lnurl/luds/blob/luds/16.md)),
 the domain will be used to make the first lnurlp call to somevasp.com.
 
@@ -16,3 +16,11 @@ the domain will be used to make the first lnurlp call to somevasp.com.
 (including the $).
 
 The UMA SDKs validate these requirements and will throw an error if they are not met.
+
+## Lightning Address Inter-op
+
+UMA addresses are valid Lightning Addresses when the leading $ is stripped. Receiving VASPs who choose to support
+plain LNURL-PAY transactions (which is a subset of UMA) should treat an incoming LNURLP request to a receiver
+without a leading $ as a request to pay the receiver directly via LNURL-PAY. This way, users can still have a
+single user name compatible with both UMA and LNURL, while keeping a clear distinction between the two for cases
+where a VASP has to understand regulatory requirements.