For events held by Apache projects, clearance needs to be obtained. Clearance is granted by VP, Brand (Shane Curcuru) usually in response to an email to trademarks@apache.org with a description of what is being requested. This is a private email list. The request should reference any discussion that has happened on dev and private lists to give complete context. For a list of events such as the continually ongoing NetBeans Days, a blanket request is fine assuming that the (P)PMC has been involved, i.e., the committers on the NetBeans Apache dev mailing list. A description of the events and the involvement of the (P)PMC is what VP, Brand will use to either approve or ask more questions. Casual get-togethers with no commercial sponsors are easier to get approval for, which is exactly what the NetBeans Days are.
Note: From an Apache point of view what's important (besides trademarks being respected) is that all organizations are treated fairly and that it's clear that they cannot "own" the event or project. Making sure we don't favor commercial entities or organizations over others is a strong requirement of the ASF's 501c(3) status, so we're very picky about that. And besides this legal requirement, it's what makes the ASF a unique place where companies which might compete in the market can collaborate in a fair way, due to our very neutral status.
For publicizing NetBeans events, the Apache News posts at https://blogs.apache.org/foundation/ could mention those events, best is to contact press@apache.org for that. Apache has an Event Listing (https://events.apache.org/), that we'd also like to make use of.