security: add IBM to distributors, clarify policy. (envoyproxy#7781)

Signed-off-by: Harvey Tuch <[email protected]>

SECURITY.md

@@ -329,7 +329,8 @@ customers, of which approximately 400 are using Seven in production. [links]
 We announce on our blog all upstream patches we apply to "Seven." [link to blog
 posts]
 
-> 4. Not be a downstream or rebuild of another distribution.
+> 4. Not be a downstream or rebuild of another distribution. If you offer Envoy as a publicly
+>    available infrastructure or platform service, this condition does not need to apply.
 
 This does not apply, "Seven" is a unique snowflake distribution.
 
@@ -376,6 +377,7 @@ CrashOverride will vouch for the "Seven" distribution joining the distribution l
 | [email protected]     | Cloud Foundry |
 | [email protected]                      | Datawire      |
 | [email protected] | Google        |
+| [email protected]                       | IBM           |
 | [email protected]          | Istio         |
 | [email protected]                       | Red Hat       |
 | [email protected]                    | solo.io       |