It's not "iK", because that tag is intended for terms where an incorrect kanji is used, but the usage is common enough to record it. An example is writing お買い徳 instead of お買い得.
Whether 咒い should have "oK" is a hard call. I'd lean towards not having it as it's a rare itaiji rather than an old/obsolete form. I'm not too fussed either way.

Just saw Rene's comment under 呪い(のろい).
Also note that Kangxi has 呪 but not 咒 (see Wiktionary for instance),
so 呪 is the original form and 咒 is a variant.
Not sure what the best way to handle this is,
but I lean towards [oK].

KanjiDic koj wiktionary

咒 seems to be an alternative form of 呪.
KanjiDic lists it with the reading まじな.う

@@ -9 +9 @@
-<ke_inf>&iK;</ke_inf>
+<ke_inf>&oK;</ke_inf>

Daijr, Daijs

Added iK tag as per n-gram hits above.

"curse" seems to fit (part of) the definition given in Diajr and Daijs.

"magic formula" is unclear.

@@ -8,0 +9 @@
+<ke_inf>&iK;</ke_inf>
@@ -19 +20 @@
-<gloss>magic formula</gloss>
+<gloss>curse</gloss>